An environmental sensing device (ESD) is a device which actuates after sensing an appropriate velocity change by mechanically integrating an acceleration input over time. ESDs have applications, for example, for use in automotive airbags and for seat belt tensioners. Current ESDs are generally based on fluid or mechanical dampening. Fluid-damped ESDs can be problematic due to thermal expansion of the fluid that must be accommodated, and which can lead to eventual fluid leakage. Mechanically-damped ESDs require precision machining and piece-part assembly.
The present invention is a microelectromechanical ESD (also referred to herein a MEM apparatus or a MEM switch) which utilizes eddy-current damping to integrate an acceleration input over time thereby eliminating leakage problems and thermal expansion issues of conventional fluid-damped ESDs. The present invention can also be fabricated using MEM fabrication technologies such as surface and bulk micromachining and LIGA (an acronym based on the first letters for the German words for lithography, electroplating and injection molding) which have been extensively developed in recent years. Such MEM fabrication technologies utilized for the MEM apparatus of the present invention eliminate the need for conventional precision machining and can largely or entirely eliminate the need for piece-part assembly. Additionally, such MEM fabrication technologies utilized for the MEM apparatus of the present invention can provide size and weight reduction benefits as well as batch fabrication advantages.
These and other advantages of the present invention will become evident to those skilled in the art.